The area covered by a cellular telecommunications network is divided into a plurality of cells. Each cell is served by a base transceiver station. Mobile stations are arranged to communicate with the base transceiver station of the cell with which the mobile station is associated. The communications between the base station and the mobile station is by means of a wireless connection.
It has been proposed that the cellular network be used in order to determine the location of a mobile station and hence the user thereof. In particular, the cell in which the mobile station is located can be identified and hence an estimate of the position of the mobile station and its user can be obtained.
Using this information, it has been proposed that location dependent services or information can be provided to a user. For example, a user may need to find the nearest ATM (automatic teller machine). Banks often operate in an international environment, i.e. the same services are available in many countries. The service provider (in this case the Bank) may have information about ATM's and their locations for example for the whole Scandinavian area. The location service may be a WAP (wireless application protocol) service.
Problems arise when a mobile station roams in a different network. This different network is referred to as the visited network. A subscriber generally subscribes to one network, the home network, but can use his mobile station in areas not covered by his home network. This is permitted where agreements exist between the home network and the visited network. The home and visited network are often operated by different network operators. Where cell information is provided by the mobile station, this information has to be converted to a more usable format, such as geographical coordinates, country or city name, postal address etc before it can be used by the WAP location dependent service. This is because the WAP location service is not able to associate the cell identity with a geographical location. Usually, the conversion of the cell identity into geographic information can be made by using cell information maintained by a network operator. This information is usually confidential or is difficult for anyone except the operator to keep up to date. Accordingly, one operator may not have information about another operator's cells and the associated geographic information. In other words, when the mobile station is visiting another network, it may not be possible to provide geographic information associated with a cell identity. Without this geographic information, it is not possible to provide a location dependent service. In the case of the example discussed previously, when for example, a Finnish person requests the service in Stockholm, the home operator cannot convert the cell identity of the Finnish person into geographical information because the cell identity values are from another operator's network. The Finnish person can therefore not receive information on the location of the nearest ATM.